Australian studies point this out.
Add to that that the bad guys still get guns.
Mentioned the other day that the Brit NHS has been paying doctors NOT to refer people to hospitals for further tests, including cancer patients. Let's not forget that they've also been using the Liverpool Care Pathway for quite some time. You know, the protocol under which some doctor decides you're too old or too disabled to be worth saving, so they leave you to die of thirst and starvation. Out of 'compassion'. But mostly because "You don't make enough of a contribution to society to be worth saving, so just hurry up and die."
I was reminded of something the other day over on Bookface: no matter how many times you point out the facts, idiots keep insisting "NO BACKGROUND CHECKS AT GUN SHOWS! NO BACKGROUND CHECK TO BUY GUNS ON THE INNERNETS!"